Abstract
Hydrogen embrittlement has become an important subject of study in order to guarantee the necessary safety and reliability during the service life of many steel components. In this context, the aim of this study is to evaluate the effect of hydrogen on the fracture toughness of a 42CrMo4 steel quenched and tempered at 700 °C. The influence of hydrogen was assessed by means of fracture toughness tests carried out on SENB specimens under two different conditions: 1) pre-charged with gaseous hydrogen in a pressurized reactor at 19.5 MPa and 450 °C for 21 h, and 2) in-situ cathodic H-charging. The influence of displacement rate, density current and electrolyte composition was also evaluated in order to determine their influence in the fracture toughness of the steel. Fracture toughness results were significantly lower under in-situ charging as hydrogen absorption was greatly enhanced due to the high plastic deformation induced in the crack tip region of the specimen. On the other hand, the lower is the applied displacement rate, the stronger is the fracture toughness reduction, as more time is available for hydrogen accumulation and embrittlement. Finally, SEM analysis was performed to differentiate the operative failure micromechanisms.